1. Field of The Invention
This invention relates to toners for electrophotographic process. More particularly, it relates to toners for electrophotographic process which contain a specific complex salt compound.
2. Description of Prior Art
Electrophotographic (imaging) process referred to as xerographic imaging process or xerography are well known (U.S. Pat. No. 4,066,563, etc.).
General method for electrostatic image formation is as follows: That is, first, toners are charged by contact friction with glass beads, iron powders, aluminum powders, etc. called carriers, then these toners are allowed to develop an electrostatic latent image on a photoconductor comprising a photoconductive material (such as selenium, zinc oxide or cadmium sulfide) and the visible image thus obtained is fixed by heating or treating with solvents, vapor. Toners are usually composed of a binder as a main component and a charge control agent, a colorant, etc. and are pulverized to 1-50.mu. in particle size. Quality characteristics required for toners are chargeability, durability of charge (an ability to maintain a charge for a long time), flowability, etc. Especially, chargeability and durability of charge which have close relation with adherence property of toners to a transfer base (e.g., paper) are very important properties for image formation.
As positive charge control agents among charge control agents used in toners, there have been widely known nigrosine dyes, quaternary ammonium salts, pyridinium salts, etc. and as negative charge control agents, there have been widely known Cr, Co metal complex dyes, nitrohumic acid, etc. (cf. The Journal of Electrosatic Society, 1980, Vol. 4, No. 3, Page 144).
When Cr, Co metal complex dyes are used as negative charge control agents, chargeability reaches a tolerable level, but since these complex dyes are water-soluble, they are poor in compatibility with binders and the resulting toners are high in hygroscopicity and low in durability of charge. Thus, they are inferior in repetition preperty in image formation (copy).
Furthermore, toners disclosed in Japanese Patent Kokai (Laid-open) Nos. 93457/84 and 35142/81 are fairly improved in these properties, but are still insufficient in improvement of chargeability and durability of charge.